Corrosion preventing agent



2,783,202 Ice Patented Feb. 26,1957

CORROSION PREVENTING AGENT John P. McDermott, Springfield, N. J., assignor to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Application May 20, 1955, Serial No. 510,019

8 Claims. (Cl. 25246.6)

The present invention relates to the improvement of hydrocarbon products derived from petroleum sources and more particularly to the preparation of improved mineral lubricating oil compositions by the incorporation therein of a new class of additives which impart improved properties to such hydrocarbon products.

This application is a continuation-inpart of patent application Serial No. 192,617, filed on October 27, 1950 and now abandoned.

In the development of petroleum lubricating oils the trend has been to use more and more efficient refining methods in order to reduce the tendency of the oils to form carbon and deposits of solid matter or sludge. While such highly refined oils possess many advantages, their resistance to oxidation, particularly under conditions of severe service, is generally decreased and they are more prone to form soluble acidic oxidation products which are corrosive. They are generally less eifective than the untreated oils in protecting themetal surfaces which they contact against rusting and corrosion due to oxygen and moisture. Although generally superior to lightly refined oils they may deposit films of varnish on hot metal surfaces, such as the pistons of internal combustion engines, under very severe engine operating conditions.

In accordance with the present invention a new class of compounds has been discovered which when added to refined lubricating oils in small proportions substantially reduce the tendency of such oils to corrode metal surfaces,

and which are particularly effective in inhibiting the corrosion of copper-lead and cadmium-silver bearings. They are likewise effective in inhibiting oxidation of such oils and other petroleum hydrocarbon products, as will be more fully explained hereinafter.

The new class of materials which have been found to possess the antioxidant and stabilizing qualities described above are oil-soluble reaction products of sulfur-containing-organo-substituted dithiophosphoric acids and epoxides. Such products may be defined broadly by the formula R S R: s

OH RO I la h where R is a sulfurized aliphatic hydrocarbon radical, and where one of the symbols R1, R2, R3, and R4 represents hydrogen, an aliphatic hydrocarbon radical containing 1 to 4 carbon atoms, or a phenyl radical and the at least 4 carbon atoms and more preferably at least 6 carbon atoms per radical. Examples of unsaturated alcohols which may be sulfurized and employed to prepare the compounds of the present invention include methylvinylcarbinol, crotyl alcohol, allyl carbinol, penten-l-ol-S, hexenol, octenol, nonenol, undecenol, oleyl alcohol, geraniol, citronellol, and the reaction products of butadiene monoxide with saturated alcohols. Monoolefin and diolefin alcohols having about 4 to 22, and preferably about 10 to 18 carbon atoms per molecule may be used. Monoolefin alcohols are preferred. Oleyl alcohol is particularly preferred. The sulfurization of these alcohols may be carried out by heating the unsaturated alcohol, or mixtures thereof, with elemental'sulfur.

Reaction temperature of about to 200 '0, preferably about 150 to 180 C., and reaction times of about 0.2 to 2 hours, preferably about 0.5 to 1.5 hours, may be used. It is preferred to use suflicient sulfur in the reaction to introduce about one atom of sulfur into each molecule of the alcohol. A stoichiometric excess of sulfur may be employed to assure completion of this reaction. Sulfurization catalysts such as Zinc oxide, .pentarnethylene diarnine dithiocarbamate and the like may be employed if desired.

The dithiophosphoric acids may be prepared by reacting a sulfurized unsaturated alcohol with phosphorus pentasulfide by means well known in the art, and it is to be understood that the invention applies not only to simple acids but to mixtures of acids formed by reacting phosphorus pentasulfide with mixtures of sulfurized unsaturated alcohols, such, for example as the mixtures of sulfurized oleyl alcohol and sulfurized geraniol. The reaction of the sulfurized alcohols with P285 may be carried out with stirring of the reactants at a temperature of about to 175 0., preferably about to C., using about four moles of the alcohol per mole of P285. The completion of the reaction may be noted visually and will be indicated by the dissolution of the P285. The reaction time required will generally be in the range of about 0.5 to 5 hours, usually about 1 to 2 hours. After the reaction is completed the reaction prodnet is preferably blown with nitrogen or other inert gas to remove hydrogen sulfide therefrom. If desired the reaction may be carried out in a solvent such as a mineral oil, e. g. a'mineral lubricating oil.

The epoxides which may be reacted with the dithiophosphoric acids in accordance with this invention include especially the well-known alkylene oxides having 2 to 6 carbon atoms, preferably 2 to 4 carbon atoms per molecule, such as ethylene oxide, propylene oxide, the butylene and isobutylene oxides, and butadiene monoxide, also styrene oxide.

The reaction between the dithiophosphoric acid and the epoxide is a spontaneous exothermic reaction which takes place immediately upon contact of the reactants at normal room temperatures, and may be conveniently conducted by adding about one mole of the epoxide slowly to one mole of the dithiophosphoric acid while rapidly stirring the reaction mixture and controlling the temperature by means of a Water or ice bath. Generally temperatures in the range of about 20 to 100 C. may be employed. No catalyst is required, and the time required for the completion of the reaction is not gneater than two hours and is usually much less. Reaction times of about 0.2 to 2 hours may generally be employed. Solvents are not normally required, but in some cases it may be convenient to conduct the reaction in the presence of well known inert solvents such as ethylene dichloride, benzene, xylene, or a mineral oil.

The amount of the additives of the present invention which is to be employed in mineral lubricating oil compositions or other petroleum hydrocarbon compositions (which generally will contain a major proportion of the petroleum hydrocarbon oil) will normally range from about 0.02% to more generally from about 0.1 to about 2% by weight, based on the total composition, and the particular amount in individual cases will be selected in accordance with the requirements of the case and in view of the properties of the base stock employed. For commercial purposes, it is convenient to prepare concentrated oil solutions in which the amount of additive in the composition ranges from 25 to 50% by weight, and to transport and store them in such form. In preparing a lubricating oil composition for use as a crankcase lubricant the additive concentrate is merely blended with the base oil in the required amount.

The preparation and testing of the additives of the present invention are illustrated in the examples described below, but it is to be understood that these specific examples are not to be construed as limiting the scope of the invention in any manner.

Example 1.-Di-(sulfurized oleyl) dithiophosphoric acid-ethylene oxide reaction product Sulfurized oleyl alcohol was prepared by heating a solution of 268 g. (1.0 mol) of oleyl alcohol in 268 g. of a light mineral oil with 32 g. (1.0 mol) of sulfur at 165 C. for one hour with rapid stirring.

The oil solution of sulfurized oleyl alcohol was then heated with 55.5 g. (0.25 mol) of P285 at 145 C. for 1 /2 hours followed by filtration to remove a small amount of unreacted P285. The filtrate was then blown with nitrogen on the steam bath for 20 minutes. The product was an approximately 50% oil solution of di- (sulfurized oleyl) dithiophosphoric acid.

The filtrate was placed in a 4-necked, 2 liter flask equipped with a stirrer, thermometer, reflux condenser, and gas inlet tube. Ethylene oxide was then passed into the stirred solution for 2 hours, keeping the temperature below 30 C. by means of an ice bath. The reaction product was then blown with nitrogen on the steam bath for 20 minutes, a clear, reddish liquid was obtained which analyzed 2.0% phosphorus and 8.8% sulfur.

Example 2.S. O. D. corrosion test A blend was prepared containing 0.25% by weight of the di-(sulfurized oleyl) dithiophosphoric acid-ethylene oxide reaction product prepared in Example I in a paraf finic mineral lubricating oil of SAE 20 grade. This blend and a sample of the unblended base oil were submitted to a corrosion test, known as the S. O. D. corrosion test, designed to measure the elfectiveness of the product in inhibiting the corrosiveness of a typical mineral lubricating oil toward the surfaces of copper-lead bearings. The test was conducted as follows: 500 cc. of the oils was placed in a glass oxidation tube (13 inches long and 2 /8 inches in diameter) fitted at the bottom with a A inch air inlet tube perforated to facilitate air distribution. The oxidation tube was then immersed in a heating bath so that the oil temperature was maintained at 325 F. during the test. Two quarter sections of automotive bearings of copper-lead alloy of known Weight having a total area of 25 sq. cm. were attached to opposite sides of a stainless steel rod which was then immersed in the test oil and rotated at 600 R. P. M., thus providing sufficient agitation of the sample during the test. Air was then blown through the oil at the rate or" 2 cu. ft. per hour. At the end of each 4-hour period the bearings were removed, washed with naphtha and weighed to determine the amount of loss by corrosion. The hearings were then repolished (to increase the severity of the test), reweighed, and then subjected to the test for ad- Oil or oil blend Bearing corrosion life (hrs) Base 011 9 Base oil +0.25% product of Example 1 27 Thus it will be noted that the addition of only 0.25 wt. percent of the product of Example I increased the hearing corrosion life threefold.

The products of the present invention may be employed not only in ordinary hydrocarbon lubricating oils but also in the heavy duty type of lubricating oils which have been compounded with such detergent type additives as metal soaps, metal petroleum sulfonates, metal phenates, metal alcoholates, metal alkyl phenol sulfides, metal organo phosphates, phosphites, thiophosphates, and thiophosphites, metal xanthates and thioxanthates, metal thiocarbamates, and the like. Other types of additives, such as phenols and phenol sulfides, may also be present.

The lubricating oil base stock used in the compositions of this invention may be straight mineral lubricating oils or distillates derived from paraffinic, naphthenic, asphaltic or mixed base crudes, or, if desired, various blended oils may be employed as well as residuals, particularly those from which asphaltic constituents have been carefully removed. The oils may be refined by conventional methods using acid, alkali and/or clay or other agents such as aluminum chloride, or they may be extracted oils produced by solvent extraction with solvents such as phenol, sulfur dioxide, etc. Hydrogenated oils or white oils may be employed as well as sythetic oils resembling petroleum oils, prepared, for example, by the polymerization of olefins or by the reaction of oxides of carbon with hydrogen or by the hydrogenation of coal or its products.

For the best results the base stock chosen should normally be an oil which with the new additive present gives the optimum performance in the service contemplated. However, since one advantage of the additives is that their use also makes feasible the employment of less satisfactory mineral oils, no strict rule can be laid down for the choice of the base stock. The additives are normally sufficiently soluble in the base stock, but in some cases auxiliary solvent agents may be used. The lubricating oils will usually range from about 40 to 150 seconds (Saybolt) viscosity at 210 F. The viscosity index may range from 0 to or even higher.

Other agents than those which have been mentioned may be present in the oil composition, such as dyes, pour point depressants, heat thickened fatty oils, sulfurized fatty oils, sludge dispersers, antioxidants, thickeners, viscosity index improvers, oiliness agents, resins, rubber, olefin polymers, and the like.

Assisting agents which are particularly desirable as plasticizers and defoamers are the higher alcohols having preferably 8-20 carbon atoms, e. g. octyl alcohol, lauryl alcohol, stearyl alcohol, and the like.

In addition to being employed in lubricants, the additives of the present invention may also be used in other petroleum oil products such as motor fuels, heating oils, hydraulic fluids, torque converter fluids, cutting oils, flushing oils, turbineoils, transformer oils, industrial oils, process oils, and the like, and generally as antioxidants in mineral oil products. They may also be used in gear lubricants, greases and other products containing mineral oils as ingredients.

What is claimed is:

1. A petroleum'hydrocarbon product containing dissolved therein a corrosion inhibiting amount of an oil soluble compound of the formula where R is a sulfurized aliphatic hydrocarbon radical; and where one of the symbols R1, R2, R3, and R4 represents a member of the group consisting of hydrogen, aliphatic hydrocarbon radicals containing 1 to 4 carbon atoms, and phenyl radicals and the others of the symbols R1, R2, R3 and R4 represent hydrogen atoms.

2. A composition according to claim 1 in which R contains in the range of 4 to 22 carbon atoms.

3. A composition according to claim 1 in which R contains about one sulfur atom.

4. A composition according to claim 1 in which R containsabout one sulfur atom and in the range of 10 to 18 carbon atoms.

5. A lubricating oil composition comprising a major proportion of a mineral lubricating oil and a minor, corrosion inhibiting amount of a compound of the formula R S H H where R is a sulfurized oleyl radical.

6. A composition according to claim 5 wherein said minor amount is about 0.02 to 5% by weight, based on the total composition.

7. An additive concentrate consisting essentially of a mineral lubricating oil and about 25 to by weight of an oil soluble compound of the formula R0 S H H d am-Lon RO/ 1'1 where R is a sulfurized oleyl radical.

References Cited in the file of this patent UNITED STATES PATENTS 2,531,129 Hook et a1 Nov. 21, 1950 

1. A PETROLEUM HYDROCARBON PRODUCT CONTAINING DISSOLVED THEREIN A CORROSION INHIBITING AMOUNT OF AN OIL SOLUBLE COMPOUND OF THE FORMULA 